This invention relates to pneumatic tires with track belts and more particularly to an improved removable track belt pneumatic tire constructed of a removable track belt mounted on an improved radially reinforced beaded tire carcass that is typically for use with earthmoving vehicles.
The track belt pneumatic tires of the present invention are generally designed for use on large earthmover vehicles and are subjected to high stress and loads under harsh environmental conditions such as in rock quarries, mines, foundries, and other areas where tires are subjected to puncture-producing and wear-inducing conditions.
As discussed in U.S. Pat. No. 4,351,380, certain prior art track belt tire assemblies comprise a plurality of ground-engaging shoes spaced about the periphery of the supporting structure. The heavy loads on the shoes result in great stresses being developed that sometimes lead to premature tire failure. The U.S. Pat. No. 4,351,380 is directed to an improved track belt assembly which comprise a plurality of shoes spaced about the periphery of a load-supporting structure and secured to a reinforcing belt structure disposed on the side of the shoe opposite the ground-engaging side thereof.
The large pneumatic tires, which are typically used for earthmoving vehicles, sometimes fail due to the high stress and loads caused by the harsh environmental conditions in which they are operated. These large prior art pneumatic tires had a greater tendency to fail in one of three tire locations or areas than because of other sources of failure. The first problem area was that the turnup end of the ply would sometimes break through the sidewall of the tire. A second problem area was a tire failure in the bead area. The third problem area was a tendency to fail in the upper shoulder area of the tire.
In the prior art, conventional solutions to these problems include increasing the gauge of the sidewall to increase the bending stiffness, increasing bead area stiffness and robustness, and decreasing tire deformation under load by increasing the sidewall stiffness. To further improve tire durability, the ply turnup portion of tires was typically reinforced.
In U.S. Pat. No. 4,609,023, having a common assignee with the present invention, the sidewall inserts were incorporated in the tire carcass to allow the ply structure to conform to its natural shape when the tire is inflated.
With the continual drive to improve earthmover performance, there is a continuing need to provide novel methods and tire designs for improving earthmover tire durability. The present invention is directed to an improved pneumatic tire and removable track belt assembly with which the frequency of premature tire failure is thought to be substantially reduced. The present invention is also directed to providing an improved pneumatic tire and track belt assembly which is designed to allow large tires to be transported in several sections and then assembled at the construction site to ease the otherwise difficult problem of transporting the large tires, i.e. sometimes over 13 feet in height and approximately 8,000 to 15,000 pounds. Moreover, the present invention relates to an improved pneumatic tire and removable track belt assembly with which the driving characteristics of the tire can be more economically changed and the inventory of the number of tire spares that are typically needed can be reduced.
It is an object of the present invention to provide a pneumatic tire for an earthmover vehicle, the pneumatic tire being as defined in one or more of the appended claims and, as such, having the capability of being constructed to accomplish one or more of the following subsidiary objects.
It is another object of the present invention to provide an improved tire and removable track belt assembly for an earthmover vehicle wherein the frequency of premature tire failure has been substantially reduced.
Another object of the present invention is directed to providing an improved tire and removable track belt assembly which is designed to allow large tires to be transported in several sections and then assembled at the delivery site.
Still another object of the present invention is to provide an improved tire and removable track belt assembly with which the driving characteristics of the tire can be quickly and economically changed.
Yet another object of the present invention is to provide an improved tire and removable track belt assembly with which the number of tire spares that are stored in inventory can be reduced.
Still another object of the present invention is to provide an improved tire and removable track belt assembly with a carcass ply turnup configuration that supports the turnup ends under high deflection forces.
A further object of the present invention is to provide an improved tire and removable track belt assembly with a carcass ply turnup configuration that enables the rim flanges to support the turnup ends under high deflection forces.
A still further object of the present invention is to provide an improved tire and removable track belt assembly wherein the ply line of a carcass ply layer follows the natural ply line.
In accordance with an embodiment of the invention, an improved track belt tire includes a removable tread belt assembly mounted to the outer circumferential surface of an inflatable, multi-layered tire carcass, The tire carcass comprises a plurality of ply layers, a pair of spaced apart bead wires, and a pair of sidewall portions extending from the bead wires to the outer circumferential surface of the multi-layered tire carcass. A first carcass ply is embedded within the multi-layered tire carcass and extends entirely about the circumference of the tire with turnup ends looped around and extending axially outwards from the bead wires. The outermost ends of the turnup ends are located radially outward at a distance equal to between about 2 and 3 times the diameters of the bead wires as measured from the intersection of a centerline extending through the center of bead wires and a line tangent to the most radially inward surface of the carcass ply where the carcass ply turnup ends loop around the wire beads to a line perpendicular to the centerline and tangent to the outer ends of the ply turnup ends.
Further in accordance with an embodiment of the invention, the track belt pneumatic tire further includes first, second, third, and fourth apex elements disposed radially above each of the bead wires with the first of the apex elements being located adjacent each of the bead wires, the second of the apexes being located between overlying sides of the turnup ends of the carcass ply, the third of the apexes being located between the section of the inner surface of the carcass ply as it approaches the bead wires and the axially inner sides of the turnup ends of the carcass and the fourth of the apexes being located against the outer sides of the turnup ends of the carcass ply so that the turnup ends are encased within the second and fourth apexes.
Still further in accordance with an embodiment of the invention, the first apex is constructed of a first elastomer which is stiffer than a second elastomer from which the second, third and fourth of the apexes are constructed. The first elastomer that is at least 20% to about 50% stiffer than the second elastomer from which the second, third and fourth of the apexes are constructed.
Further yet in accordance with an embodiment of the invention, the track belt pneumatic tire includes an interlocking structure to secure the removable tread belt assembly to the tire carcass. The interlocking structure includes interlocking belt structure on the inner surface of the removable tread belt assembly for engaging complementary interlocking support structure on the outer circumferential surface of the inflatable tire carcass.
According to the invention, the interlocking tread structure comprises a plurality of circumferentially extending lands and grooves; and the interlocking support structure comprises a plurality of circumferentially extending lands and grooves oriented to engage complementary ones of the circumferentially extending lands and grooves on the inner surface of the removable tread belt assembly to prevent axial movement of the removable tread belt assembly with respect to the outer circumferential periphery of the inflatable load support structure.
According to the invention, the ply line of the carcass ply layer follows the natural ply line. That is, the angle of approach of the carcass ply towards the wire beads is substantially parallel to the axially interior surface of the rim flange when the tire is inflated to a normal operating pressure.